In following, the present invention is described exemplary with regard to lighting systems as an example for a system comprising power consuming devices and with regard to lighting devices as the power consuming devices. However, it has to be pointed out that the present invention can be applied correspondingly also to further systems having power consuming devices like heating systems or air conditioning systems, for example, or to a combination of such systems, for example, a system comprising lighting devices, heating devices and air conditioning devices.
Lighting systems are known to consume a large proportion of energy or power in buildings and, more generally, in city infrastructures and may be seen as cause for high energy or power consumption. Therefore, lighting systems are often configured as controllable loads to offer dynamic load control services such as demand response in smart grids. By implementing lighting systems as controllable loads, by control of which it is ensured that the consumed electrical load or power consumption is less than what can be generated and/or provided, lighting systems may provide load/demand reductions or restorations to the smart grid.
In current lighting systems, lamps or lighting devices are often uniformly and simultaneously dimmed by use of dimmable ballasts for a period of time. Thereto, simple power line broadcasting mechanisms may be used for controlling (dimming) the lamps or lighting devices of the lighting systems.
The amount of electricity generated and transmitted by the electricity grid must match at any time the electricity consumed by loads at the other end of the grid to ensure stability of the electricity grid. In known control systems, this is mainly achieved by adjusting the electricity generation to match the actual consumption. However, in several periods of time (e.g., during hot summer days), the electricity demand exceeds the generation capacity (e.g., due to intensive operating of air conditioning systems). Curtailment is then deployed to ensure that the grid can still deliver power generated under the available generation capacity.
Usually, curtailment is done by the grid operator by manually disconnecting a distribution branch of the grid, deeming all loads served by the branch unusable during the curtailment period. Alternatively, grid customers can selectively and individually disconnect some loads from the grid. However, coordination and agreement between the grid customers and the grid operators on factors like the amount and duration of reduction, for example, is required. This necessitates reliable communication means between the grid operator and the customers. Furthermore, incentives and settlements may be needed to reward the customers. Hence, this approach is applicable only to a handful of large utility customers, typically, large industrial customers, which can supply a significant amount of reduction.
Due to the recent rapid developments in the area of communications technology, it is possible to connect a vast number of customers to the grid operator to deploy an orchestrated load shedding. Also economically, it has become more feasible to develop such infrastructure as the gap between the available generation and peak demand widens, driving up electricity or power costs. Currently, a number of demand response programs are operational in various states of the USA (e.g. California, Texas, New York), supplying reduction of the peak demand. Demand response will play an even more important role in the future Smart Grid to balance an increasingly dynamic grid due to growing integration of highly variable renewable energy or power resources.
On the facility level, participation in the demand response program requires actively controlling the load to ensure meeting the targeted demand reduction. Active load control may also benefit facilities not taking part in the demand response program as it can reduce the total cost of the consumed electricity or power. For instance, many utility companies also apply peak demand charge based on the peak power consumption during the billing period in addition to the charge for the energy consumption. Proper control of peak demand may reduce costs of electricity incurred by user(s). Active load control may also be used to take advantage of dynamic tariff pricing.
US 2010/0088261 A1 refers to a method of load shedding to reduce the total power consumption of a load control system.